There are certain electrical systems having a plurality of power sources and a plurality of power consuming devices that require switches to connect the power sources to the consuming devices in any desired order. A specific system having these requirements is the electrical system of a boat needing D.C. power to start the engine and D.C. power to operate the radio, navigational devices, etc. If the boat has only one bank of batteries, or two banks selectable by use of a conventional marine battery selector switch for these tasks, it frequently occurs that starting the engine draws so much power from the batteries that the high-tech microprocessor-controlled navigational components are temporarily without power due to the voltage drop, causing the memory systems of the components to die. Generally, this situation is avoided by using at least two sources of power, one of which is dedicated to provide the engine starting power and the other is used for the electrical/ electronic equipment on board. This, of course, requires that two banks of batteries be kept fully operational at all times. If one bank loses its power, the equipment it energizes is left useless and there is no reserve power unless the leads are changed so as to utilize the fully charged batteries for energizing devices not intended to be served by those charged batteries. This problem is discussed in "Practical Sailor", Jan. 15, 1989, Vol. 15, No. 2, where the solutions suggested are to use two battery selector switches to isolate the loads, thus providing a separate battery for the electronic equipment, called "loran", or to build a complicated electronic circuit including a diode/ capacitor time sensitive surge arrester arrangement (although this will not provide the protection, if the engine starting takes a long time).
It is an object of this invention to provide a single hand-operated switch which can directly replace existing conventional marine battery switches and can be mounted any place convenient to the operator and connected to the electrical system so as to provide separate circuits for the engine starter and the electronic equipment using separate sources of power, and yet can be switched to use any source for any consuming device. Furthermore, for emergencies, the switch can connect all power sources to all power consuming devices or either source to both consuming devices, particularly useful when a bank of batteries fails.
It is another object to provide such a switch which will handle large current loads, while being vapor-proof and spark-proof. Still other objects will be evident from the more detailed description which follows.